The present invention relates generally to the dressing and sharpening of grinding wheels, and more particularly to an improved method of dressing and sharpening and to an arrangement for carrying out the method.
It is already known from the art to dress and sharpen grinding wheels or discs. Diamond grinding wheels, and those which contain cubically-crystalline boron nitride as the grinding substance, have heretofore always been dressed and sharpened in two separate operating stages. Firstly, the wheel is dressed, for instance using silicone-carbide wheels as the dressing wheels, in order to restore the geometric configuration of the grinding wheel to the original shape. Subsequently the grinding wheel must be sharpened, for which a separate operation was heretofore required. Usually, a very soft silicone-carbide dressing wheel of a corundum dressing wheel were used, to remove binder material from the grinding wheel in order to expose diamond chips or boron nitride crystals of the grinding wheel which are bound by the binding material.
It is evident that it would be desirable to carry out both of these operations in a single step. Heretofore, this appeared impossible of achievement, because it is known that an increase in the dressing or cutting speed v will result in a decrease of the cutting or dressing ability F and in an increase in the temperature T resulting from the friction. If the wear S.sub.B of the grinding wheel is to be considered in dependence upon the dressing speed v, then it is found in practice that the minimum wear is obtained at a certain specific dressing speed, the minimum wear being usually represented as the value v.sub.A. If the dressing speed v is increased beyond the minimum wear value v.sub.A, or is decreased substantially below this value, this results in a substantial increase of the grinding wheel wear S.sub.B.
These factors are true both of grinding operations in general, and of the dressing of a grinding wheel in particular, and it follows from them that the dressing of a grinding wheel should be carried out either at very high or at very low dressing speeds v. However, contrary to this general assumption it has been found that dressing at high dressing speeds v does not produce satisfactory results because of the strong increase which takes place in the temperature prevailing in the area where dressing is carried out, that is where material is being removed. This temperature increase is, inter alia, the result of expansion of the dressing tool and of the thermal stresses which act upon the grinding wheel itself. Conversely, dressing at very low dressing speeds is also disadvantageous because as a general rule the equipment available for the dressing operation is not particularly sophisticated and not provided with arrangements for reducing the rotations of the grinding wheel to the extent necessary to obtain such low dressing speeds.